Die casting production involves a number of steps that requires careful implementation in getting the best output from the process. Improper execution of any of these steps can result in a defective casting product. It is highly important to avoid any die casting defects, since repairing them is a rather expensive option.
The two major die casting defects are surface quality and porosity. Surface area defects are a key die casting issue that is caused by numerous factors like wall thickness, die temperature, laminations, and oxide skins. Let us look into these factors in brief.
Wall Thickness
The thickness of different walls yields different results. A thin wall can result in the alloy flow to freeze and aid in a much quicker cold flow. The fill time is subjected to a significant change by different wall thicknesses. For a wall that has thickness that ranges from 2.0 and 1.5 millimeters, there is a 25 percent reduction in the fill time.
The temperatures of the die are also vital in thin wall casting, as the reduced mass of the part is insufficient in providing the sufficient heat required for the die.
Die Temperature
Die temperature can have a noteworthy effect on the surface area defects. A lower die temperature can cool the metal stream fluid, thereby affecting surface defects by increasing the quantity of solidified metal in the fluid metal stream.
Insufficient percent amount of solid will result in the stream to become stiff and solid, which causes the flow to form cold-flow wrinkles. Cycle time is another key aspect of die temperature, and it should be maintained constantly to control the die casting defects.
Laminations
Metal flow conditions like the resting of one flow on top of another results in laminations. This is a common defect in die casting process and is caused by the way the metal flows inside the casting. This layering effect is also affected by the geometry of the casting. To overcome this problem, it is good to decrease the fill time since it is the most effective.
Moreover, increasing the die and metal temperatures can also help in dealing with the problem. Laminations are also caused by die flexing that result in an additional layer of metal on the exterior of the original casting skin.
Oxide Skins
The presence of oxide skins also aids in causing lamination. They are created in the holding furnace or during the injection process in the cold chamber. For corrective oxide skins, an appropriate skimming of the holding pot would do well along with reducing the time in the cold chamber. Other measures include filtering, fluxing, and degassing.